JP2008156465A - Water-based ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink for inkjet recording excellent in storage stability, to provide a water dispersion for inkjet recording used for the ink, and to provide a cross-linked polymer particle. <P>SOLUTION: The cross-linked polymer particle for inkjet recording is provided, in which the cross-linked polymer particle contains an organic pigment (A) and a pigment derivative (B) having a polar group and is the cross-linked polymer particle obtained by cross-linking the polymer with a compound having two or more of the reactive functional group in the molecule. The water dispersion for ink jet recording containing it and the water-based ink are provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to crosslinked polymer particles for inkjet recording, and an aqueous dispersion and an aqueous ink containing the same.

The ink jet recording system is a recording system in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle and attaching them to a recording member. This method is widely spread because it is easy to make full color and is inexpensive, and has many advantages such as the ability to use plain paper as a recording member and non-contact with the object to be printed.
Among them, from the viewpoint of weather resistance and water resistance of printed materials, those using pigment-based ink as a colorant have become mainstream (for example, see Patent Document 1).

Patent Document 1 discloses a microencapsulation in which pigment particles having an anionic group on the surface are coated with a cationic polymerizable surfactant and a polymer having a repeating structural unit derived from a hydrophobic monomer or a crosslinkable monomer. An inkjet recording ink containing a pigment and an aqueous dispersion thereof is disclosed.
However, the water-based ink containing the above pigment dispersion is not satisfactory in terms of storage stability.

JP 2005-120136 A

  An object of the present invention is to provide an aqueous ink for inkjet recording excellent in storage stability, an aqueous dispersion for inkjet recording used for the ink, and a crosslinked polymer particle.

The present invention provides the following (1) to (3).
(1) A crosslinked polymer particle containing an organic pigment (A) and a pigment derivative (B) having a polar group, wherein the crosslinked polymer particle is a compound having two or more reactive functional groups in the molecule. Crosslinked polymer particles for inkjet recording, which are crosslinked polymer particles obtained by crosslinking a polymer.
(2) An aqueous dispersion for inkjet recording, containing the crosslinked polymer particles according to (1).
(3) A water-based ink for ink-jet recording containing the water dispersion according to (2).

  The water-based ink containing the crosslinked polymer particles for ink jet recording and the aqueous dispersion of the present invention is excellent in storage stability.

The present invention is a crosslinked polymer particle containing an organic pigment (A) and a pigment derivative (B) having a polar group, which is obtained by crosslinking a polymer with a compound having two or more reactive functional groups in the molecule. By using the aqueous dispersion containing the crosslinked polymer particles obtained, the crosslinked polymer particles for inkjet recording can be made into an aqueous ink for inkjet recording excellent in storage stability.
The cross-linked polymer particles containing the organic pigment (A) and the pigment derivative (B) having a polar group hinder the aggregation and crystal growth of the organic pigment dispersion, and improve the storage stability of the resulting aqueous ink. Can do.
Hereinafter, each component used for this invention is demonstrated.

(Organic pigment (A))
Examples of the organic pigment (A) used in the present invention include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthoraquinone pigments, and quinophthalone pigments. Is mentioned.
Specific examples of preferred organic pigments include C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed. Said organic pigment can be used individually or in mixture of 2 or more types in arbitrary ratios.
Among these, when an azo pigment derivative described later is used, C.I. I. Pigment yellows 74 and 97, Hanza pigments, C.I. I. Insoluble azo pigments such as benzimidazolone pigments such as CI Pigment Yellow 151; I. Condensed azo pigments such as CI Pigment Yellow 93 and 128; I. Polycyclic pigments such as isoindolinone pigments such as CI Pigment Yellow 110 are preferable. I. Pigment yellow 74, C.I. I. Pigment Yellow 97 and the like are preferable.
Moreover, an organic pigment and an extender can also be used together as needed. Examples of extender pigments include silica, calcium carbonate, and talc.

(Pigment derivative having polar group (B))
The pigment derivative (B) having a polar group used in the present invention (hereinafter sometimes simply referred to as “pigment derivative (B)”) has a function as a surface treatment agent for an organic pigment, and the organic pigment (A) It is used to improve the dispersion stability.

Examples of the polar group include one or more selected from the group consisting of a sulfonic acid group, a carboxy group, a phosphoric acid group, a sulfinic acid group, an amino group, an amide group, and an imide group. Among these, a sulfonic acid group is preferable from the viewpoint of dispersion stability.
The pigment derivative (B) having a polar group is the same or similar mother skeleton as the organic pigment (A) from the viewpoint of improving the adsorptivity to the surface of the organic pigment (A), mixing / dispersing stability with the polymer, and hue. It is preferable to have.

The pigment derivative (B) having the same or similar mother skeleton is based on the same or similar molecular structure as the organic pigment (A).
Examples of the method for producing the pigment derivative (B) having the same or similar mother skeleton include, for example, (i) a method of introducing a polar group using the reactivity of the compound after synthesizing the compound of the organic pigment (A) (Ii) A method of synthesizing the pigment derivative (B) having a polar group introduced at the same time as the synthesis of the organic pigment (A).
Examples of the pigment derivative (B) having such a structure include azo pigment derivatives and polycyclic pigment derivatives.
The azo pigment derivative can be obtained by (1) a method of synthesizing a ketimine pigment derivative by reacting an organic pigment molecule with an aliphatic amine, and (2) a mixed coupling method.
(2) The mixed coupling method involves coupling by mixing a diazo component or a heterogeneous coupler component into which a polar group is introduced and a diazo component or a coupler component of the pigment matrix during the synthesis of an azo pigment by an azo coupling reaction. This is a reaction method. The mixed coupling method can simultaneously synthesize an organic pigment and a pigment derivative, and can also serve as a surface treatment step for the organic pigment. From this viewpoint, a mixed coupling method is preferable as a method for producing the azo pigment derivative.
Examples of the polycyclic pigment derivative include compounds in which a polar group is introduced into a benzene nucleus in the chemical structure of an organic pigment. The polar group may be introduced by being directly substituted on the benzene nucleus, or may be introduced through a linking group such as an alkyl group.
The pigment derivatives are described in detail in “Pigment Dispersion Technology” (Technical Information Association, February 24, 1999, first printing), pages 85-88.

  As the pigment derivative (B), one or more azo compounds represented by the following formula (1) (hereinafter simply referred to as “azo compounds”) are preferable from the viewpoint of improving dispersion stability.

(Wherein R ¹⁰ and R ²⁰ represent an aryl group having 6 to 50 carbon atoms which may have a substituent, and may be the same or different. At least one of R ^{10 and} R ²⁰ is It has a polar group.)
In formula (1), the aryl group preferably has 6 to 40 carbon atoms, more preferably 6 to 30 carbon atoms, and the preferred substituent is an alkoxy group having 1 to 22 carbon atoms, preferably 1 to 12 carbon atoms. An alkyl group having 1 to 22 carbon atoms, preferably 1 to 12 carbon atoms, ether group, ester group, nitro group, hydroxyl group, halogen group, amide group, amino group, carboxy group, sulfonic acid group, sulfuric acid group, phosphoric acid Group, phosphonic acid group, sulfoxide group (—SO—), sulfone group (—SO ₂ —), triazine group (one or two protons removed from triazine) and the like. In addition, Formula (1) can also be represented by the following formula (2) as an isomer.

As said azo compound, what introduce | transduced the polar group into at least one aryl group as a hydrophilic dispersibility provision group is used. Examples of the polar group include the same groups as described above. Among these, from the viewpoint of dispersion stability, —SO ₃ M, —COOM, —SO ₂ M, —RSO ₂ M, —PO ₃ HM, —PO ₃ M (wherein M is a hydrogen atom, R represents an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent. One type or two or more types of functional groups selected from the group consisting of the functional group represented by formula (1) or a salt thereof are preferably exemplified, and a sulfonic acid group is more preferable.
Examples of the pigment derivative (B) having a sulfonic acid group include sulfonic acids and metal salts thereof such as sodium, aluminum and calcium, and ammonium, octadecylammonium, didodecylammonium, dimethyloctadecylammonium, dimethyldioctadecylammonium, and benzyldimethyloctadecyl. Examples thereof include pigment derivatives having ammonium salts such as ammonium.

Examples of the pigment derivative (B) having a polar group include C.I. which is an insoluble azo pigment. I. Pigment yellow 74, C.I. I. Pigment Yellow 97 pigment derivative is preferred.
Specific examples of the azo compound represented by the above formula (1) and a method for producing the azo compound are known methods, for example, JP-A Nos. 2003-253188, 2004-182952, and No. 3055673. Specific examples and manufacturing methods described can be given. Particularly preferred specific examples include compounds of the following formulas (3) and (4). Moreover, when introducing a sulfonic acid group into an organic pigment, the organic pigment can be reacted with a sulfonating agent such as concentrated sulfuric acid, fuming sulfuric acid or chlorosulfuric acid.

The above-mentioned organic pigment (A) and pigment derivative (B) (hereinafter sometimes referred to as “coloring agent” together) are either a single component or a mixture of two or more of (A) and (B). Can be used.
The weight ratio of the organic pigment (A) to the pigment derivative (B) is 1 to 30 parts by weight of the pigment derivative (B) with respect to 100 parts by weight of the organic pigment (A) from the viewpoint of dispersion stability, color tone, and the like. Is preferable, 1 to 20 parts by weight is more preferable, and 1 to 10 parts by weight is still more preferable. When the weight ratio is 1 part by weight or more, the number of adsorption points on the surface of the organic pigment (A) is increased, and the dispersion stability is improved. On the other hand, when it is 30 parts by weight or less, the pigment derivative (B) that is not adsorbed on the surface of the organic pigment (A) is reduced, and the storage stability is improved.
When the organic pigment (A) and the pigment derivative (B) are mixed, they may be synthesized and mixed in the same synthesis tank, or the organic pigment (A) and the pigment derivative (B) are synthesized separately, and then You may mix in any processes, such as a drying process, a grinding | pulverization process, a classification process, and a pigment dispersion process. From the viewpoint of obtaining a colorant with a uniform primary particle diameter and enhancing the initial dispersion stability, it is preferable to synthesize both in the same synthesis tank.

The content of the colorant in the aqueous dispersion and the water-based ink of the present invention is preferably 1 to 30% by weight, more preferably 2 to 20% by weight, from the viewpoint of enhancing dispersion stability and printing density. % Is more preferable.
The weight ratio of the polymer to the colorant (polymer / colorant) used in the present invention is preferably 10/90 to 90/10, and preferably 20/80 to 80/20 from the viewpoint of increasing the print density. More preferably, it is more preferably 20/80 to 50/50.

(polymer)
The polymer used in the present invention is cross-linked with a cross-linking agent to form a cross-linked polymer, and is preferably a water-insoluble polymer. A water-insoluble polymer is a polymer having a dissolution amount of 10 g or less, preferably 5 g or less, more preferably 1 g or less when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C. Say. When the polymer has a salt-forming group, the dissolution amount is a dissolution amount when the salt-forming group of the polymer is neutralized 100% with acetic acid or sodium hydroxide according to the type.
Examples of the polymer to be used include polyester, polyurethane, and vinyl polymer. From the viewpoint of dispersion stability, a vinyl polymer obtained by addition polymerization of a vinyl monomer (vinyl compound, vinylidene compound, vinylene compound) is preferable.

(Vinyl polymer)
As the vinyl polymer, (a) a salt-forming group-containing monomer (hereinafter sometimes referred to as “(a) component”), (b) a macromer (hereinafter sometimes referred to as “(b) component”) and / or (c ) A water-insoluble vinyl polymer obtained by copolymerizing a monomer mixture (hereinafter also referred to as “monomer mixture”) containing a hydrophobic monomer (hereinafter also referred to as “component (c)”) is preferable. This water-insoluble vinyl polymer has a structural unit derived from the component (a), a structural unit derived from the component (b) and / or a structural unit derived from the component (c). A more preferred water-insoluble vinyl polymer has a structural unit derived from the component (a) or a structural unit derived from the components (a) and (c) as a main chain, and a structural unit derived from the component (b) as a side chain. It is a water-insoluble graft polymer.

((A) salt-forming group-containing monomer)
(A) The salt-forming group-containing monomer is used from the viewpoint of enhancing the dispersion stability of the resulting dispersion. Examples of the salt-forming group include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group.
Examples of the salt-forming group-containing monomer include cationic monomers and anionic monomers described in JP-A-9-286939, paragraph [0022].
Representative examples of the cationic monomer include unsaturated amine-containing monomers and unsaturated ammonium salt-containing monomers. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N′-dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferable.
Representative examples of anionic monomers include unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers, and the like.
Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxy Examples thereof include ethyl phosphate.
Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoints of dispersion stability and ejection stability.

((B) Macromer)
(B) The macromer is used from the viewpoint of enhancing the dispersion stability of the polymer particles containing the colorant. The macromer includes a macromer which is a monomer having a polymerizable unsaturated group having a number average molecular weight of 500 to 100,000, preferably 1,000 to 10,000. In addition, the number average molecular weight of (b) macromer is measured using polystyrene as a standard substance by gel chromatography using chloroform containing 1 mmol / L of dodecyldimethylamine as a solvent.
Among (b) macromers, from the viewpoint of dispersion stability of polymer particles containing a colorant, styrene macromers and aromatic group-containing (meth) acrylate macromers having a polymerizable functional group at one end are preferable. .
Examples of the styrenic macromer include a styrene monomer homopolymer or a copolymer of a styrene monomer and another monomer. Examples of the styrene monomer include styrene, 2-methylstyrene, vinyl toluene, ethyl vinyl benzene, vinyl naphthalene, chlorostyrene, and the like.

Examples of the aromatic group-containing (meth) acrylate-based macromer include a homopolymer of an aromatic group-containing (meth) acrylate or a copolymer thereof with another monomer. As an aromatic group-containing (meth) acrylate, an arylalkyl having 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, more preferably 7 to 12 carbon atoms, which may have a substituent containing a hetero atom. (Meth) acrylate having an aryl group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a group or a substituent containing a hetero atom In addition, examples of the substituent containing a hetero atom include a halogen atom, an ester group, an ether group, and a hydroxy group. Examples include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, and benzyl (meth) acrylate is particularly preferable.
The polymerizable functional group present at one end of the macromer is preferably an acryloyloxy group or a methacryloyloxy group, and the other monomer to be copolymerized is preferably acrylonitrile.
The content of the styrene monomer in the styrene macromer or the aromatic group-containing (meth) acrylate in the aromatic group-containing (meth) acrylate macromer is preferably 50% by weight from the viewpoint of increasing the affinity with the pigment. As mentioned above, More preferably, it is 70 weight% or more.

(B) The macromer may have a side chain composed of another structural unit such as an organopolysiloxane. This side chain can be obtained, for example, by copolymerizing a silicone macromer having a polymerizable functional group at one end represented by the following formula (5).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} O] _{t -Si (CH 3) 3 (} 5)
(In the formula, t represents a number of 8 to 40).
Examples of commercially available styrenic macromers as component (b) include Toa Gosei Co., Ltd. trade names, AS-6 (S), AN-6 (S), HS-6 (S), and the like. It is done.

((C) hydrophobic monomer)
(C) The hydrophobic monomer is used from the viewpoint of improving the printing density. Examples of the hydrophobic monomer include alkyl (meth) acrylates and aromatic group-containing monomers.
As the alkyl (meth) acrylate, those having an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms are preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meta) ) Acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) Examples include decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, and (iso) stearyl (meth) acrylate.
In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present. Indicates. “(Meth) acrylate” indicates acrylate, methacrylate, or both.

The aromatic group-containing monomer has an aromatic group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a substituent containing a hetero atom. Vinyl monomers are preferable, and examples thereof include the styrene monomer (c-1 component) and the aromatic group-containing (meth) acrylate (c-2 component). The above-mentioned thing is mentioned as a substituent containing a hetero atom.
Among the components (c), a styrene monomer (c-1 component) is preferable from the viewpoint of improving printing density, and styrene and 2-methylstyrene are particularly preferable as the styrene monomer. The content of the component (c-1) in the component (c) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density.
Moreover, as an aromatic group containing (meth) acrylate (c-2) component, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, etc. are preferable. The content of the component (c-2) in the component (c) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density and gloss. Moreover, it is also preferable to use (c-1) component and (c-2) component together.

((D) hydroxyl group-containing monomer)
The monomer mixture may further contain (d) a hydroxyl group-containing monomer (hereinafter sometimes referred to as “component (d)”). (D) The hydroxyl group-containing monomer exhibits an excellent effect of enhancing dispersion stability.
As the component (d), for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n represents the average number of added moles of oxyalkylene group. The same)) (meth) acrylate, polypropylene glycol (n = 2-30) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1-15)) (meth) acrylate, etc. Can be mentioned. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferable.

((E) monomer represented by formula (6))
The monomer mixture may further contain (e) a monomer represented by the following formula (6) (hereinafter sometimes referred to as “(e) component”).
CH ₂ = C (R ¹ ) COO (R ² O) _q R ³ (6)
Wherein R ¹ is a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, R ² is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³ is , A monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, q means an average number of added moles, and represents a number of 1 to 60, preferably 1 to 30. )
(E) component expresses the outstanding effect of improving discharge property.
In the formula (6), examples of the hetero atom include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.
Preferable examples of R ¹ include methyl group, ethyl group, (iso) propyl group and the like.
Preferred examples of the R ² O group include an oxyethylene group, an oxytrimethylene grave, an oxypropane-1,2-diyl group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, and two or more kinds thereof. Examples thereof include oxyalkanediyl groups having 2 to 7 carbon atoms (oxyalkylene groups).
Preferable examples of R ³ include an aliphatic alkyl group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, an alkyl group having 7 to 30 carbon atoms having an aromatic ring, and Examples thereof include an alkyl group having 4 to 30 carbon atoms and having a heterocycle.

  Specific examples of the component (e) include methoxypolyethylene glycol (1 to 30: the value of q in the formula (2), the same applies hereinafter) (meth) acrylate, methoxypolytetramethylene glycol (1 to 30) ( (Meth) acrylate, ethoxy polyethylene glycol (1-30) (meth) acrylate, octoxy polyethylene glycol (1-30) (meth) acrylate, polyethylene glycol (1-30) (meth) acrylate 2-ethylhexyl ether, (iso) Propoxy polyethylene glycol (1-30) (meth) acrylate, butoxypolyethylene glycol (1-30) (meth) acrylate, methoxypolypropylene glycol (1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol) Polymerization) (1 to 30, ethylene glycol therein: 1-29) (meth) acrylate. Among these, octoxypolyethylene glycol (1-30) (meth) acrylate and polyethylene glycol (1-30) (meth) acrylate 2-ethylhexyl ether are preferable.

Specific examples of commercially available (d) and (e) components include Shin-Nakamura Chemical Co., Ltd. polyfunctional acrylate monomer (NK ester) M-40G, 90G, 230G, and Nippon Oil & Fats Co., Ltd. BLEMMER series, PE-90, 200, 350, PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800 , 50PEP-300, 50POEP-800B, 43PAPE600B, and the like.
The components (a) to (e) can be used alone or in admixture of two or more.

The content of the components (a) to (e) in the monomer mixture (content as an unneutralized amount; the same applies hereinafter) or the water-insoluble vinyl polymer (a) to (e) ) The content of the structural unit derived from the component is as follows.
The content of component (a) is preferably 2 to 40% by weight, more preferably 2 to 30% by weight, and particularly preferably 3 to 20% by weight from the viewpoint of dispersion stability of the resulting dispersion.
The content of the component (b) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, particularly from the viewpoint of enhancing the interaction with the pigment.
The content of the component (c) is preferably 5 to 98% by weight, more preferably 10 to 60% by weight, from the viewpoint of improving print density.
The content of component (d) is preferably 5 to 40% by weight, more preferably 7 to 20% by weight, from the viewpoint of dispersion stability of the resulting dispersion.
The content of the component (e) is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, from the viewpoint of improving dischargeability.
The total content of [component (a) + component (d)] in the monomer mixture is preferably 6 to 60% by weight, more preferably 10 to 50% by weight, from the viewpoint of dispersion stability of the resulting dispersion. is there. The total content of [component (a) + component (e)] is preferably 6 to 75% by weight, more preferably 13 to 50% by weight, from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. . Moreover, the total content of [(a) component + (d) component + (e) component] is preferably 6 to 60% by weight, more preferably from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. 7 to 50% by weight.
The weight ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 to 1, more preferably from the viewpoint of dispersion stability and print density of the resulting dispersion. Is 0.02 to 0.67, more preferably 0.03 to 0.50.

(Manufacture of polymers)
The polymer is produced by copolymerizing a monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
The solvent used in the solution polymerization method is not particularly limited, but a polar organic solvent is preferable. When the polar organic solvent is miscible with water, it can be used by mixing with water. Examples of the polar organic solvent include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol and propanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate and the like. Among these, methanol, ethanol, acetone, methyl ethyl ketone, or a mixed solvent of one or more of these and water is preferable.
In the polymerization, azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), t-butyl peroxyoctate, dibenzoyl oxide, etc. Known radical polymerization initiators such as organic peroxides can be used.
The amount of the radical polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per mol of the monomer mixture.
In the polymerization, a known polymerization chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol and thiuram disulfide may be further added.

Since the polymerization conditions of the monomer mixture vary depending on the type of radical polymerization initiator, monomer, and solvent used, it cannot be determined unconditionally. Usually, the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C, and the polymerization time is preferably 1 to 20 hours. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. Further, the obtained polymer can be purified by repeating reprecipitation or by removing unreacted monomers and the like by membrane separation, chromatographic method, extraction method and the like.

The weight average molecular weight of the polymer is preferably from 5,000 to 500,000, more preferably from 10,000 to 400,000, further preferably from 10,000 to 300,000, from the viewpoints of glossiness and dispersion stability of the colorant. ˜300,000 is particularly preferred. In addition, the weight average molecular weight of the polymer was measured by the method shown in the Examples.
When the vinyl polymer has a salt-forming group derived from (a) a salt-forming group-containing monomer, it is neutralized with a neutralizing agent. As the neutralizing agent, an acid or a base can be used depending on the type of the salt-forming group in the polymer. For example, hydrochloric acid, acetic acid, propionic acid, phosphoric acid, sulfuric acid, lactic acid, succinic acid, glycolic acid, gluconic acid, glyceric acid and other acids, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine , Bases such as trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine, and tributylamine.

The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 150%, and particularly preferably 50 to 150%.
Here, the degree of neutralization can be determined by the following formula when the salt-forming group is an anionic group.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100
When the salt-forming group is a cationic group, it can be determined by the following formula.
{[Weight of neutralizer (g) / equivalent of neutralizer] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]} × 100
The acid value and amine value can be calculated from the structural unit of the polymer. Alternatively, it can also be determined by a method in which a polymer is dissolved in an appropriate solvent (for example, methyl ethyl ketone) and titrated.

(Crosslinking agent)
In the present invention, a compound having two or more reactive functional groups in the molecule (hereinafter also simply referred to as “crosslinking agent”) is used in order to appropriately crosslink the polymer. The molecular weight of the cross-linking agent is preferably 120 to 2000, more preferably 150 to 1500, and particularly preferably 150 to 1000, from the viewpoint of easy reaction and storage stability of the resulting cross-linked polymer particles.
The number of reactive functional groups in the cross-linking agent is preferably 2 to 4 and most preferably 2 from the viewpoint of improving the gloss by controlling the molecular weight. The reactive functional group is preferably at least one selected from the group consisting of a hydroxyl group, an epoxy group, an aldehyde group, an amino group, and a carboxy group.

Specific examples of such a crosslinking agent include the following (a) to (e).
(A) Compound having two or more hydroxyl groups in the molecule: for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, 1,4-butanediol, 1,5-pentanediol 1,6-hexanediol, neopentyl alcohol, diethanolamine, tridiethanolamine, polypropylene glycol, polyvinyl alcohol, pentaerythritol, sorbitol, sorbitan, glucose, mannitol, mannitan, sucrose, glucose and the like.
(B) Compound having two or more epoxy groups in the molecule: for example, polyglycidyl such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether ether.
(C) Compounds having two or more aldehyde groups in the molecule: for example, polyaldehydes such as glutaraldehyde and glyoxal.
(D) Compounds having two or more amino groups in the molecule: for example, polyamines such as ethylenediamine and polyethyleneimine.
(E) Compounds having two or more carboxy groups in the molecule: for example, polyvalent carboxylic acids such as oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid and adipic acid.
Among these, (b) a compound having two or more epoxy groups in the molecule is preferable, and trimethylolpropane polyglycidyl ether is particularly preferable.

The polymer has a reactive group (crosslinkable functional group) capable of reacting with the crosslinking agent, and a suitable combination example of both is as follows.
When the reactive group of the polymer is an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group, the crosslinking agent is preferably the compounds (a), (b), and (d).
When the reactive group of the polymer is an amino group, the crosslinking agent is preferably the compounds (b), (c) and (e).
When the reactive group of the polymer is a hydroxyl group, the crosslinking agent is preferably the compounds (c) and (e).
When the reactive group of the polymer is an isocyanate group or an epoxy group, the crosslinking agent is preferably the compounds (a), (d) and (e).
Among the above combinations, from the viewpoint of controlling the polymer so as to impart an appropriate cross-linked structure, one or more reactions selected from an acidic group (carboxy group, sulfonic acid group, phosphoric acid group, etc.) and an amino group A combination of a polymer having a functional group and (b) a compound having two or more epoxy groups in the molecule is particularly preferred.

As the reactive group (crosslinkable functional group) capable of reacting with the crosslinking agent, a polymer having an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group, an amino group, a hydroxyl group, an isocyanate group, an epoxy group, etc. In the production of the polymer, it can be produced by copolymerizing a polymerizable monomer composition containing the monomer having the reactive group.
As the polymer having a reactive group capable of reacting with the crosslinking agent, the polymer having a salt-forming group such as an acidic group or an amino group can be a polymer obtained by copolymerizing the aforementioned salt-forming group-containing monomer. As the polymer having, a polymer obtained by copolymerizing the above-mentioned hydroxyl group-containing monomer can be used.
As the polymer having an epoxy group, a monomer having an epoxy group, specifically, a polymer obtained by copolymerizing glycidyl (meth) acrylate can be used. As the polymer having an isocyanate group, (i) a monomer having an isocyanate group, for example, a polymer copolymerized with isocyanate ethyl (meth) acrylate, (ii) an isocyanate-terminated prepolymer obtained from an unsaturated polyester polyol and isocyanate was copolymerized. A polymer or the like can be used.

(Crosslinked polymer particles containing organic pigment (A) and pigment derivative (B))
Crosslinked polymer particles containing the organic pigment (A) and the pigment derivative (B) (hereinafter sometimes referred to as “colorant-containing crosslinked polymer particles”) are used to improve the dispersion stability and print density of the pigment. .
From the viewpoint of storage stability, the method for producing the crosslinked polymer particles is obtained in Step I and Step I in which polymer particles containing an organic pigment and a pigment derivative are obtained using an organic pigment, a pigment derivative and a polymer. A method of producing the crosslinked polymer particles by mixing the polymer particles containing the organic pigment and the pigment derivative with the crosslinking agent to crosslink the polymer to obtain crosslinked polymer particles is preferable.

The manufacturing method by the said process I and the process II can be performed by the following process (1)-(3), for example.
Step (1): Step of obtaining a dispersion of polymer particles containing a colorant by dispersing a mixture containing a polymer, an organic solvent, an organic pigment, a pigment derivative, water, and, if necessary, a neutralizing agent Step (2) ): Step of removing the organic solvent from the dispersion obtained in step (1) to obtain an aqueous dispersion of polymer particles containing a colorant Step (3): Colorant obtained in step (2) Cross-linking the polymer particles containing the polymer with a cross-linking agent to obtain an aqueous dispersion of cross-linked polymer particles containing the colorant

In step (1), the polymer is first dissolved in an organic solvent, and then an organic pigment, a pigment derivative, water, and, if necessary, a neutralizing agent and a surfactant are added to the obtained organic solvent solution. And mixing to obtain an oil-in-water dispersion. In the mixture, the colorant is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, the organic solvent is preferably 10 to 70% by weight, more preferably 10 to 50% by weight, and the polymer is 2 to 2% by weight. It is preferably 40% by weight, more preferably 3 to 20% by weight, and water is preferably 10 to 70% by weight, more preferably 20 to 70% by weight.
When the polymer has a salt-forming group, it is preferable to use a neutralizing agent. There is no particular limitation on the degree of neutralization when neutralizing with a neutralizer. Usually, it is preferable that the liquid dispersion of the finally obtained water dispersion is neutral, for example, pH is 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the polymer. Examples of the neutralizing agent include those described above. Further, the polymer may be neutralized in advance.
Examples of the organic solvent include alcohol solvents such as ethanol, isopropanol and isobutanol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and diethyl ketone, and ether solvents such as dibutyl ether, tetrahydrofuran and dioxane. Preferably, the amount dissolved in 100 g of water at 20 ° C. is preferably 5 g or more, more preferably 10 g or more, more specifically preferably 5 to 80 g, more preferably 10 to 50 g, especially Methyl ethyl ketone and methyl isobutyl ketone are preferred.

There is no restriction | limiting in particular in the dispersion method of the mixture in process (1). Although the average particle size of the polymer particles can be atomized only by the main dispersion until the desired particle size is reached, it is preferably pre-dispersed and then subjected to main dispersion by further applying a shear stress to obtain the average particle size of the polymer particles. It is preferable to control the diameter to a desired particle diameter. 5-50 degreeC is preferable and dispersion | distribution of a process (1) has more preferable 10-35 degreeC.
When preliminarily dispersing the mixture, a commonly used mixing and stirring device such as an anchor blade can be used. Among the mixing and stirring apparatuses, Ultra Disper [Asada Steel Corporation, product name], Ebara Milder [Ebara Manufacturing Co., Ltd., product name], TK Homomixer, TK Pipeline Mixer, TK Homojetter, TK Homomic Line Flow, High-speed agitating and mixing devices such as Filmix [above, Primix Co., Ltd., trade name], Clear Mix [M Technique Co., Ltd., trade name], and KD Mill [Kinetic Dispersion, Inc., trade name] are preferred.
As means for applying the shear stress of this dispersion, for example, a kneader such as a roll mill, a bead mill, a kneader, an extruder, a high-pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name), a minilab 8.3H type (Rannie Co., trade name) Representative homovalve type high-pressure homogenizer, microfluidizer (Microfluidics, trade name), nanomizer (Nanomizer, trade name), optimizer (Sugino Machine Co., trade name), Genus PY (Shiramizu Chemical Co., Ltd.) Product name], DeBEE2000 [Japan EE Co., Ltd., product name] and the like chamber type high-pressure homogenizer. A plurality of these devices can be combined. Among these, a high-pressure homogenizer is preferable from the viewpoint of reducing the particle size of the pigment.

In the step (2), an aqueous dispersion of polymer particles containing a colorant can be obtained by distilling off the organic solvent from the obtained dispersion by a known method to form an aqueous system. The organic solvent in the aqueous dispersion containing the obtained polymer particles is preferably substantially removed, but may remain as long as the object of the present invention is not impaired, and may be removed again after crosslinking as necessary. . The amount of residual organic solvent is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.
The obtained aqueous dispersion of polymer particles containing the colorant is one in which the solid content of the polymer containing the colorant is dispersed in water as the main solvent. Here, the form of the polymer particles is not particularly limited as long as the particles are formed of at least a colorant and a polymer. For example, a particle form in which a colorant is included in a polymer, a particle form in which a colorant is uniformly dispersed in a polymer, a particle form in which a colorant is exposed on the surface of a polymer particle, and the like are included.

In step (3), the polymer of the obtained polymer particles containing the colorant is crosslinked with a crosslinking agent to obtain crosslinked polymer particles. In the step (3), from the viewpoint of storage stability, it is preferable to obtain a crosslinked polymer particle containing a colorant by mixing an aqueous dispersion of a polymer particle containing a colorant and a crosslinking agent to crosslink the polymer. .
In step (3), the catalyst, solvent, temperature, and time can be appropriately selected and determined depending on the crosslinking agent used. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the reaction temperature is preferably 40 to 95 ° C.
From the viewpoint of storage stability, the amount of the crosslinking agent used is preferably 0.3 to 15 parts by weight, more preferably 0.3 to 10 parts by weight, and 0.4 to 8.0 parts per 100 parts by weight of the polymer. Parts by weight are preferred, 0.6 to 7.5 parts by weight are more preferred, and 0.9 to 6.5 parts by weight are most preferred.
In addition, the polymer crosslinking step may be performed by mixing a dispersion of polymer particles containing the colorant obtained in step (1) and a crosslinking agent. In this case, an aqueous dispersion of crosslinked polymer particles containing a colorant is obtained by performing the step of removing the organic solvent from the dispersion of crosslinked polymer particles obtained in the crosslinking step in the same manner as in the step (2). Can be obtained.

Here, the crosslinking rate (mol%) of the crosslinked polymer particles determined by the following formula (7) is preferably 1 to 60 mol%, more preferably 2.5 to 45 mol%, from the viewpoint of storage stability. Preferably it is 3-40 mol%, Most preferably, it is 5-35 mol%.
Crosslinking rate (mol%) = [number of moles of reactive group of crosslinking agent × 100 / number of moles of reactive group capable of reacting with crosslinking agent of polymer] (7)
In Formula (7), “the number of moles of the reactive group of the crosslinking agent” is a value obtained by dividing the weight of the crosslinking agent used by the equivalent of the reactive group.

(Aqueous dispersion containing crosslinked polymer particles containing colorant and ink)
The aqueous dispersion for inkjet recording of the present invention is an aqueous dispersion containing crosslinked polymer particles containing a colorant, and can be preferably obtained by the steps (1) to (3).
The aqueous dispersion of the present invention may be used as it is as a water-based ink, but a wetting agent, a penetrating agent, a dispersant, a viscosity modifier, an antifoaming agent, an antifungal agent, and a rust-preventing agent that are commonly used in water-based inks for inkjet recording. Etc. may be added.

The colorant-containing crosslinked polymer particles and the water content in the aqueous dispersion for inkjet recording and the water-based ink are as follows from the viewpoints of glossiness and storage stability.
The content of the colorant-containing crosslinked polymer particles is preferably 1 to 20% by weight, and more preferably 2 to 15% by weight. The content of water is preferably 50 to 80% by weight, more preferably 60 to 80% by weight.
The average particle diameter of the crosslinked polymer particles in the obtained water dispersion and water-based ink is preferably 10 to 500 nm, more preferably 30 to 300 nm, and particularly preferably 50, from the viewpoint of preventing clogging of the printer nozzle and dispersion stability. ~ 200 μm. The average particle diameter is determined by the method described in the examples.
The preferred surface tension (20 ° C.) of the aqueous dispersion and aqueous ink of the present invention is preferably 30 to 70 mN / m, more preferably 35 to 68 mN / m, and more preferably aqueous ink. Is 25-50 mN / m, more preferably 27-45 mN / m.
The viscosity (20 ° C.) at a solid content of 10% by weight of the aqueous dispersion is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s, in order to obtain a good viscosity when used as a water-based ink. Further, the viscosity (20 ° C.) of the water-based ink is preferably 2 to 12 mPa · s, and more preferably 2.5 to 10 mPa · s, in order to maintain good ejection properties. The pH of the water-based ink is preferably 4-10.
The ink jet method to which the water-based ink of the present invention is applied is not limited, but is particularly suitable for a piezo ink jet printer.

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
Production Example 1 (Production of water-insoluble polymer)
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol), and 10% of 200 parts of each monomer shown in Table 1 were mixed and thoroughly replaced with nitrogen gas. A mixed solution was obtained.
On the other hand, the remaining 90% of the monomers shown in Table 1 were charged into a dropping funnel, and 0.27 part of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone and a radical polymerization initiator (2,2′-azobis (2,4-dimethyl) were added. Valeronitrile)) 1.2 parts were added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.
Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped over 3 hours. After 2 hours at 65 ° C. from the end of dropping, a solution obtained by dissolving 0.3 part of the radical polymerization initiator in 5 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 2 hours and 70 ° C. for 2 hours to obtain a polymer solution. It was.
The weight average molecular weight of the obtained polymer was measured. The results are shown in Table 1.
The weight average molecular weight was measured by a gel chromatography using dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent, using polystyrene as a standard substance. The column used was HLC-8120GPC manufactured by Tosoh Corporation.

The details of the compounds shown in Table 1 are as follows.
-Styrene macromer: manufactured by Toa Gosei Co., Ltd., trade name: AS-6 (S) (50% toluene solution, solid content 15 parts), number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group, polyethylene glycol monomethacrylate ( Ethylene oxide average added mole number = 9, terminal: methyl group): Shin-Nakamura Chemical Co., Ltd., trade name: NK ester M-90G
Polypropylene glycol monomethacrylate (propylene oxide average added mole number = 9, terminal: hydroxyl group): manufactured by NOF Corporation, trade name: BLEMMER PP-500

Synthesis Example 1 <Production Example of Colorant>
In a mixed solution of 960 g of water and 327 g of 35% hydrochloric acid, 162.6 g of 3-nitro-4-toluidine and 6.07 g of a monoazo yellow organic pigment represented by the following formula (8) are added and dispersed by stirring. It was. After adding about 700 g of ice and cooling to this dispersion, add a solution of 87 g of sodium nitrite in 130 g of water and stirring for 1 hour while maintaining the temperature at 10 ° C. or lower to eliminate excess nitrous acid with sulfamic acid. Thereafter, filtration was performed to obtain a diazotized liquid. On the other hand, after 96 g (0.706 mol) of sodium acetate was dissolved in 5300 g of water, 200.9 g of acetoacetylanilide was added and dispersed, and then 90 g of 80% acetic acid was added dropwise to adjust pH to 25 ° C. To obtain a coupler solution. To this coupler liquid, the above diazotization liquid was dropped in 120 minutes to carry out a coupling reaction. Next, the temperature was raised to 90 ° C. and heat-treated for 30 minutes, followed by filtration and washing with water to remove by-product salts and the like, followed by drying at 80 ° C. with a dryer. The dried pigment was pulverized and yellow azo pigment derivative b1 represented by the following formula (3) (compound represented by the above formula (1), molecular weight 783) and C.I. I. A colorant containing Pigment Yellow 74 (PY74) was obtained. Table 2 shows the weight ratio between the obtained pigment derivative and the organic pigment.

Synthesis Examples 2 to 6 <Production Examples of Colorant>
The monoazo yellow organic pigment represented by the above formula (8) in Synthesis Example 1 was changed to 9.1 g, 12.1 g, 18.2 g, 21.2 g, and 24.2 g in Synthesis Examples 2 to 6, respectively. Was carried out in the same manner as in Synthesis Example 1 to obtain a colorant having a weight ratio of the pigment derivative (B) and the organic pigment (A) shown in Table 2.

Examples 1-6
<Production of colorant-containing polymer fine particles>
67 parts by weight of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 233 parts by weight of methyl ethyl ketone, and then 16.8 parts by weight of neutralizing agent 1 (5N aqueous sodium hydroxide) 55%) and neutralizing agent 2 (25% aqueous ammonia solution) 7.4 parts by weight (neutralization degree 100%) and ion-exchanged water 953.0 parts were added to neutralize the salt-forming groups. 230 parts by weight of the colorant obtained in Synthesis Examples 1 to 6 to be shown was added, and dispersion treatment was performed for 1 hour at a peripheral speed of 12 m / s using an ultra apex mill manufactured by Kotobuki Industry Co., Ltd. The obtained mixture was subjected to a 5-pass dispersion treatment with a microfluidizer (trade name, manufactured by Microfluidics) at a pressure of 150 MPa.
Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure, and a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) was used. An aqueous dispersion of pigment-containing polymer particles having a solid content concentration of 22% was obtained by filtering with an attached needleless syringe having a capacity of 25 mL (manufactured by Terumo Corporation) and removing coarse particles.

<Production of colorant-containing crosslinked polymer fine particles>
200.00 parts of the obtained aqueous dispersion (9.9 parts of polymer) was put into a reaction vessel under a nitrogen atmosphere, and further, a crosslinking agent (ethylene glycol diglycidyl ether, manufactured by Nagase ChemteX Corporation, Denacol EX). -810, epoxy equivalent 113) 0.17 parts and ion-exchanged water 20.73 parts, reacting at 90 ° C. for 1.5 hours with stirring, and adjusting the concentration with ion-exchanged water to crosslink the shell part ( An aqueous dispersion (solid content concentration 20%) of pigment-containing polymer particles having a crosslinking rate of 10.0 mol% was obtained.
<Manufacture of ink>
36.28 parts of an aqueous dispersion of pigment-containing polymer particles obtained by crosslinking the obtained shell part (solid content concentration 20%), 10 parts of glycerin, 7 parts of triethylene glycol monobutyl ether (TEGMBE), Surfynol 465 (Nissin) 1 part of Chemical Industry Co., Ltd.), 0.3 part of Proxel XL2 (Avisia Co., Ltd.) and 45.42 parts of ion-exchanged water were mixed, and the resulting mixture was filtered with a 1.2 μm filter (acetylcellulose membrane, The aqueous ink shown in Table 2 was obtained by filtering with a 25 mL needleless syringe attached with an outer diameter of 2.5 cm, manufactured by Fuji Photo Film Co., Ltd., and removing coarse particles.

The average particle size was measured and the crosslinking rate was calculated as follows.
(1) Average particle diameter It measured with the laser particle analysis system ELS-8000 (cumulant analysis) of Otsuka Electronics Co., Ltd. The measurement conditions are a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and an integration count of 100. The refractive index of water (1.333) is input as the refractive index of the dispersion solvent. The measurement concentration was usually about 5 × 10 ⁻³ wt%.
(2) Calculation of crosslinking rate The crosslinking rate (mol%) of a crosslinked polymer particle is represented by a following formula.
Crosslinking rate (mol%) = [number of moles of reactive group of crosslinking agent × 100 / number of moles of reactive group capable of reacting with crosslinking agent of polymer] (7)
In the present invention, when an epoxy group is used, the calculation is performed assuming that the polymer undergoes a crosslinking reaction only with a carboxy group. Moreover, in Formula (7), "the number of moles of the reactive group of a crosslinking agent" is the value which remove | divided the weight of the crosslinking agent to be used by the epoxy equivalent.
In Example 1, 9.9 parts of polymer are reacted with 0.17 part of Denacol EX-810 (epoxy equivalent 113). Therefore, the number of moles of the reactive group of the crosslinking agent is 0.17 / 113 = 0.015.
Here, since the crosslinking agent (Denacol EX-810) reacts with the carboxy group, the number of moles of the reactive group that can react with the crosslinking agent that the water-insoluble polymer has is methacrylic acid (molecular weight 86) mole that the water-insoluble polymer has. Is a number. Since methacrylic acid contained in 9.9 parts of polymer is 13% by weight,
The number of moles of methacrylic acid = 9.9 × 0.13 / 86 = 0.150.
Therefore, the crosslinking rate of the polymer particles is 0.0015 × 100 / 0.0150 = 10.0 (mol%).

Comparative Example 1
In Example 1, the colorant obtained in Synthesis Example 1 was used as an organic pigment C.I. I. The same procedure as in Example 1 was performed except that the pigment yellow was changed to Pigment Yellow 74 (PY74).
Comparative Example 2
In Example 1, it carried out like Example 1 except not having performed crosslinking reaction.

The water-based inks obtained in Examples 1 to 6 and Comparative Examples 1 and 2 were evaluated by conducting the following storage stability test. The results are shown in Table 2.
[Evaluation of storage stability]
The ink described in Table 2 was filled in a glass sealed container, and the average particle size after storage at 70 ° C. for 1 week was measured using a particle size measuring device (trade name: ELS-8000, manufactured by Otsuka Electronics Co., Ltd.) under the above conditions. The particle size increase rate was measured from the following formula (the value closer to 100% is better in storage stability) and evaluated according to the following criteria.
○: Particle size increase rate is less than 130% ×: Particle size increase rate is 130% or more Particle size increase rate = [average particle size after storage (70 ° C., particle size after 1 week storage) / average particle before storage Diameter (particle diameter before storage)] × 100

  From Table 2, it can be seen that the water-based inks of Examples 1 to 6 have a lower particle size increase rate and excellent storage stability than Comparative Examples 1 and 2.

Claims (9)

  A crosslinked polymer particle containing an organic pigment (A) and a pigment derivative (B) having a polar group, wherein the crosslinked polymer particle is crosslinked with a compound having two or more reactive functional groups in the molecule. Cross-linked polymer particles for inkjet recording, which are cross-linked polymer particles obtained as described above.   Polymer particles in which the crosslinked polymer particles contain an organic pigment (A) and a pigment derivative (B) having a polar group, and a compound having two or more reactive functional groups in the molecule (hereinafter referred to as a crosslinking agent) The crosslinked polymer particles for inkjet recording according to claim 1, which are crosslinked polymer particles obtained by mixing and crosslinking the polymer.   The crosslinked polymer particles for inkjet recording according to claim 1 or 2, wherein the weight ratio of the crosslinking agent to the polymer is 0.3 to 15 parts by weight of the crosslinking agent with respect to 100 parts by weight of the polymer. The crosslinked polymer particle for inkjet recording according to any one of claims 1 to 3, wherein the pigment derivative (B) is one or more azo compounds represented by the following formula (1).

(Wherein R ¹⁰ and R ²⁰ represent an aryl group having 6 to 50 carbon atoms which may have a substituent, and may be the same or different. At least one of R ^{10 and} R ²⁰ is It has a polar group.)   The crosslinked polymer particle for inkjet recording according to any one of claims 1 to 4, wherein the crosslinking agent is a compound having two or more epoxy groups.   The crosslinked polymer particles for inkjet recording according to any one of claims 1 to 5, wherein a crosslinking rate of the crosslinked polymer particles is 1 to 60 mol%.   The weight ratio of the organic pigment (A) and the pigment derivative (B) is 1 to 30 parts by weight of the pigment derivative (B) with respect to 100 parts by weight of the organic pigment (A). 2. Crosslinked polymer particles for ink jet recording.   An aqueous dispersion for inkjet recording, comprising the crosslinked polymer particles for inkjet recording according to any one of claims 1 to 7.   A water-based ink for ink-jet recording, comprising the water dispersion according to claim 8.